HERMANDORFER, Circuit Judge. The presence of probable cause generally permits police officers to make arrests. And as officers perform their duties, speech can play a permissible role in assessing threats and whether conduct is criminal. At the same time, police cannot use probable cause as a pretext to retaliate against individuals for protected expression. Retaliatory arrest claims arise at the crossroads of those rules. So they can trigger complex causation disputes—particularly since unlawful motive can be easy to allege and hard to disprove. Yet if left unchecked, protracted, post-arrest litigation risks chilling officers’ carrying out of important public-safety functions. The Supreme Court’s retaliatory arrest framework, set out in Nieves v. Bartlett, 587 U.S. 391 (2019), seeks to balance those concerns. Under Nieves, the presence of probable cause “generally defeat[s]” a First Amendment claim of retaliatory arrest. Id. at 406. But there’s a “narrow” out: A claim can proceed “when a plaintiff presents objective evidence that he was arrested when otherwise similarly situated individuals not engaged in the same sort of protected speech had not been.” Id. at 406-07. This case implicates the scope of that exception. At issue are officers’ arrests of Daniel and Shatina Grady during a late-night shooting investigation outside a Michigan residence. Those arrests came after the Gradys approached officers’ investigatory perimeter—set up around a suspected shooter’s location—and refused repeated commands to step back while loudly questioning the instructing officers’ authority. The district court concluded that the Gradys’ conduct gave officers probable cause to arrest them under Michigan law. Yet as the district court saw it, the Gradys’ retaliatory arrest claim fell within the Nieves exception because other onlookers had not criticized police and were not arrested. And it deemed those onlookers similarly situated to the Gradys even though they stood well outside the officers’ perimeter and had not defied officers’ commands. We conclude that the Gradys’ cited comparators were not similarly situated for purposes of satisfying the Nieves exception. Nor did the Gradys come forward with any other objective evidence sufficient to permit their claim to proceed. So Nieves’s general rule—that the presence of probable cause defeats retaliatory arrest claims—governs here. We therefore reverse the district court’s contrary decision and remand for further proceedings consistent with this opinion.